Method for controlling a powertrain of a vehicle having a dual-clutch transmission

ABSTRACT

A method for controlling a powertrain of a vehicle having a dual-clutch transmission (DCT) includes: operating the DCT while the vehicle is in motion with a high or low transmission gear drivingly engaged; receiving a shift request to engage an other one of the high and low transmission gears; reducing an engine torque output and first and second clutch torques; shifting a subtransmission to a neutral gear setting; selecting a first gear or a second gear to drive the subtransmission; shifting the main transmission to engage the selected first or second gear; after shifting the main transmission, shifting the subtransmission to the other one of the high and low transmission gears; and after shifting the subtransmission, controlling the engine torque output and the first and second clutch torques according to a driver request at an accelerator of the vehicle.

CROSS-REFERENCE

The present application claims priority to U.S. Provisional Pat.Application No. 63/304,909, entitled “Method for Controlling aPowertrain of a Vehicle Having a Dual-Clutch Transmission,” filed onJan. 31, 2022, the entirety of which is incorporated by referenceherein.

TECHNICAL FIELD

The present technology relates to methods for controlling a powertrainof a vehicle having a dual-clutch transmission.

BACKGROUND

Off-road vehicles have powertrains that can incorporate different typesof transmission, such as a continuously variable transmission (CVT) or amanually operated transmission. However, other types of transmissionscould be used in off-road vehicles and offer different performance incertain conditions than the aforementioned CVT and manually operatedtransmission.

A dual-clutch transmission (DCT) is a type of transmission that includesfirst and second clutches. The first clutch drives the odd-numberedtransmission gears via a first shaft, and the second clutch drives theeven-numbered transmission gears via a second shaft. In a DCT, gearchanges can be accomplished without interrupting torque distribution tothe driven wheels. The torque of the engine is applied to one clutch atthe same time as it is being disconnected from the other clutch. Sincealternate gear ratios can preselect an odd transmission gear on oneshaft while the vehicle is being driven in an even transmission gear(and vice versa), DCTs offer good shifting performance and efficiency incertain conditions. However, dual-clutch transmissions have not beenmade widely available in off-road vehicles yet. Reasons causing thedelay of their widespread adoption in off-road vehicles includerelatively high manufacturing costs and packaging issues due to thelimited space in the engine compartment.

Therefore, there is a desire for dual-clutch transmissions that can beefficiently packaged in an off-road vehicle, while having reducedmanufacturing costs.

SUMMARY

It is an object of the present to ameliorate at least some of theinconveniences present in the prior art.

According to an aspect of the present technology, there is provided amethod for controlling a powertrain of a vehicle, the powertraincomprising: an internal combustion engine; and a dual-clutchtransmission operatively connected to the engine, the dual-clutchtransmission comprising: a first clutch and a second clutch selectivelyactuated to transmit motion from the engine to a first shaft and asecond shaft respectively; at least one first gear mounted to the firstshaft; at least one second gear mounted to the second shaft, the atleast one first gear and the at least one second gear defining in part amain transmission of the dual-clutch transmission; and a subtransmissionoperatively connected to the main transmission, the subtransmissioncomprising: an input shaft; a high transmission gear and a lowtransmission gear mounted to the input shaft, the high transmission gearand the low transmission being selectively engageable to place thesubtransmission in a high transmission setting and a low transmissionsetting respectively; and an output shaft operatively connected to theinput shaft by a selected one of the high transmission gear and the lowtransmission gear, the method comprising: operating the dual-clutchtransmission while the vehicle is in motion with one of the hightransmission gear and the low transmission gear drivingly engaged to theinput shaft; during said operating, receiving a shift request to engagean other one of the high transmission gear and the low transmission gearto the input shaft in order to drive the output shaft with the other oneof the high transmission gear and the low transmission gear; in responseto the shift request: reducing a torque output of the engine and atorque of each of the first and second clutches; shifting thesubtransmission to a neutral gear setting whereby the output shaft isdrivingly disconnected from the input shaft; after shifting thesubtransmission to the neutral gear setting, selecting one of the atleast one first gear and the at least one second gear to drive thesubtransmission in order for the input shaft to turn, relative to theoutput shaft, at an input shaft speed according to a gear ratio thatwould be implemented between the input and output shafts by the otherone of the high transmission gear and the low transmission gear;shifting the main transmission to engage the selected one of the atleast one first gear and the at least one second gear to drive thesubtransmission; after shifting the main transmission, shifting thesubtransmission to the other one of the high transmission gear and thelow transmission gear; and after shifting the subtransmission to theother one of the high transmission gear and the low transmission gear,controlling the torque output of the engine and the torque of the firstand second clutches according to a driver request at an accelerator ofthe vehicle.

In some embodiments, the method further includes determining a targetengine speed required to maintain a speed of the vehicle when theselected one of the at least one first and the at least one second gearis drivingly engaged; and controlling the engine to change a currentengine speed to the target engine speed.

In some embodiments, the method further includes, after shifting thesubtransmission to the other one of the high transmission gear and thelow transmission gear but prior to controlling the torque output of theengine and the torque of the first and second clutches according to thedriver request: controlling the engine to change a current engine speedto approximately match a speed of the selected one of the at least onefirst gear and the at least one second gear.

In some embodiments, in response to the shift request being for engagingthe low transmission gear to the input shaft, the method furtherincludes comparing an operating speed associated with the vehicle to apredetermined speed; and denying the shift request in response to theoperating speed associated with the vehicle being greater than thepredetermined speed.

In some embodiments, in response to the shift request being for engagingthe high transmission gear to the input shaft, the method furthercomprises: comparing an operating speed associated with the vehicle to apredetermined speed; comparing the torque output of the engine to apredetermined engine torque; denying the shift request in response to:the operating speed associated with the vehicle being less than or equalto the predetermined speed; and the torque output of the engine beinggreater than the predetermined engine torque.

In some embodiments, the method further comprises, after denying theshift request, displaying an indication to a driver of the vehicleindicative of a denial of the shift request.

In some embodiments, a vehicle comprises: a frame; a driver seatconnected to the frame; a plurality of ground-engaging wheelsoperatively connected to the frame; a powertrain comprising: an internalcombustion engine supported by the frame; and a dual-clutch transmissionoperatively connected to the engine, the dual-clutch transmissioncomprising: a first clutch and a second clutch selectively actuated totransmit motion from the engine to a first shaft and a second shaftrespectively; at least one first gear mounted to the first shaft; atleast one second gear mounted to the second shaft, the at least onefirst gear and the at least one second gear defining in part a maintransmission of the dual-clutch transmission; and a subtransmissionoperatively connected to the main transmission, the subtransmissioncomprising: an input shaft; a high transmission gear and a lowtransmission gear mounted to the input shaft, the high transmission gearand the low transmission being selectively engageable to place thesubtransmission in a high transmission setting and a low transmissionsetting respectively; and an output shaft operatively connected to theinput shaft by a selected one of the high transmission gear and the lowtransmission gear, the output shaft being operatively connected to atleast one of the plurality of ground-engaging wheels; and a controllerin communication with the engine and the dual-clutch transmission, thecontroller being configured to perform the method.

In some embodiments, the vehicle is an off-road vehicle.

According to another aspect of the present technology, there is provideda method for controlling a powertrain of a vehicle, the powertraincomprising: an internal combustion engine; and a dual-clutchtransmission operatively connected to the engine, the dual-clutchtransmission comprising: a first clutch and a second clutch selectivelyactuated to transmit motion from the engine to a first shaft and asecond shaft respectively; at least one first gear mounted to the firstshaft; and at least one second gear mounted to the second shaft, themethod comprising: producing a first shift request for shifting thedual-clutch transmission from an initial gear to a different gear, theinitial gear being engaged on the first shaft, the initial gear beingone of the at least one first gear, the different gear being one of theat least one second gear; in response to the first shift request,executing a first shift sequence to shift the dual-clutch transmissionfrom the initial gear to the different gear; during execution of thefirst shift sequence, producing a second shift request for shifting thedual-clutch transmission from the different gear to the initial gear; inresponse to the second shift request: interrupting the first shiftsequence prior to the first shift sequence having finished; andexecuting a second shift sequence to reverse the first shift sequencesuch that the dual-clutch transmission engages the initial gear fordriving on the first shaft.

In some embodiments, the method further comprises, during execution ofthe first shift sequence: detecting an operational change related tooperation of the vehicle; and determining that that the operationalchange requires engagement of the initial gear; the second shift requestis executed in response to said determining.

In some embodiments, the first shift sequence comprises: engaging thedifferent gear on the second shaft; and after engaging the differentgear: decreasing a torque of the first clutch to disengage the firstclutch from the engine; and increasing a torque of the second clutch toengage the second clutch with the engine; and adjusting a speed of theengine.

In some embodiments, the first shift sequence further comprises: afteradjusting the speed of the engine and after disengaging the first clutchfrom the engine and engaging the second clutch with the engine,disengaging the initial gear on the first shaft.

In some embodiments, decreasing the torque of the first clutch todisengage the first clutch from the engine comprises decreasing thetorque of the first clutch to a kisspoint torque value of the firstclutch or lower; and increasing the torque of the second clutch toengage the second clutch with the engine comprises increasing the torqueof the second clutch to a microslip torque value of the second clutch orhigher.

In some embodiments, adjusting the speed of the engine comprises: if thedifferent gear is a higher gear than the initial gear, decreasing thespeed of the engine after the second clutch is engaged with the engine;and if the different gear is a lower gear than the initial gear,increasing the speed of the engine prior to the second clutch beingengaged with the engine.

In some embodiments, in response to the first shift sequence beinginterrupted before adjusting the speed of the engine, interrupting thefirst shift sequence comprises: stopping the decreasing of the torque ofthe first clutch before the torque of the first clutch reaches akisspoint torque value of the first clutch; and stopping the increasingof the torque of the second clutch before the torque of the secondclutch reaches a microslip torque value of the second clutch.

In some embodiments, the second shift sequence comprises: lowering thetorque of the second clutch to at least a kisspoint torque value of thesecond clutch; increasing the torque of the first clutch to at least amicroslip torque value of the first clutch; and maintaining the initialgear engaged on the first shaft.

In some embodiments, the second shift sequence further comprisesdisengaging the different gear on the second shaft.

In some embodiments, in response to the first shift sequence beinginterrupted during or after the adjusting of the speed of the engine,interrupting the first shift sequence comprises stopping the adjustingof the speed of the engine.

In some embodiments, adjusting the speed of the engine comprises: if thedifferent gear is a higher gear than the initial gear, decreasing thespeed of the engine after the second clutch is engaged with the engine;and if the different gear is a lower gear than the initial gear,increasing the speed of the engine prior to the second clutch beingengaged with the engine.

In some embodiments, the second shift sequence comprises: if thedifferent gear is a higher gear than the initial gear: increasing thespeed of the engine to a speed that is appropriate for driving theinitial gear; after increasing the speed of the engine: lowering thetorque of the second clutch to at least a kisspoint torque value of thesecond clutch; and increasing the torque of the first clutch to at leasta microslip torque value of the first clutch; and if the different gearis a lower gear than the initial gear, decreasing the speed of theengine to a speed that is appropriate for driving the initial gear.

According to another aspect of the present technology, there is provideda method for accelerating a vehicle from rest, the vehicle having apowertrain including an internal combustion engine; and an automatictransmission operatively connected to the engine, the automatictransmission including a clutch selectively actuated to transmit motionfrom the engine to a shaft; at least one gear mounted to the shaft. Themethod includes controlling the powertrain according to a first controlstrategy; while the vehicle is at rest, receiving a mode indicationindicating that a driver of the vehicle has selected a launch controlmode for accelerating the vehicle from rest; receiving a brake-onindication indicating that a braking system of the vehicle has beenactivated; determining that an accelerator of the vehicle is in a launchcontrol acceleration position; in response to receiving at least themode indication and the brake-on indication and determining that theacceleration is in the launch control acceleration position, controllingthe powertrain according to a second control strategy to limit the speedof the engine to an increased idle speed; increase a torque of theclutch to a predetermined torque value higher than the kisspoint torquevalue; while controlling the powertrain according to the second controlstrategy receiving a brake-off indication indicating that the brakingsystem has been released; in response to receiving the brake-offindication, increasing the torque of the clutch according to apredefined first ramp to drive a lowest gear of the at least one gearengaged on the shaft; determining that an amount of clutch slip is belowa predetermined first threshold; in response to the amount of clutchslip being below the predetermined first threshold, stopping limitingthe speed of the engine; and further increasing the torque of the clutchaccording to a predefined second ramp until the clutch slip is below asecond threshold.

In some embodiments, the second threshold is below the first threshold.

In some embodiments, the method further includes, in response tostopping limiting the speed of the engine, increasing engine speedaccording to a position of the accelerator.

In some embodiments, the vehicle further includes a turbochargeroperatively connected to the engine; and the increase of the speed ofthe engine to the increased idle speed causes the turbocharger toprovide additional boost pressure to the engine.

In some embodiments, the method further includes prior to receiving themode indication, determining that each of a plurality of initial modeconditions have been met; and in response to the plurality of initialmode conditions being met, enabling a mode input, the mode indicationbeing transmitted to the controller from the mode input upon selectionof the launch mode by the operator via the mode input.

In some embodiments, the method further comprises, while controlling theengine according to the second control strategy: determining that atleast one deactivation condition has been met; and in response to the atleast one deactivation condition being met, returning to a standardoperation mode whereby the powertrain is operated according to the firstcontrol strategy.

In some embodiments, determining that the at least one deactivationcondition has been met includes determining that a time limit ofcontrolling the powertrain according to the second control strategy hasbeen reached.

In some embodiments, determining that the at least one deactivationcondition has been met includes determining that the acceleratorposition has decreased from the launch control acceleration position.

In some embodiments, determining that the at least one deactivationcondition has been met includes determining that the automatictransmission has been shifted from the lowest gear of the at least onefirst gear to the lowest gear of the at least one second gear.

In some embodiments, the method further comprises, subsequent toreceiving the mode indication and prior to receiving the brake-offindication: determining that at least one pre-launch deactivationcondition has been met; and in response to the at least one pre-launchdeactivation condition being met, returning to a standard operation modewhereby the vehicle is operated according to the first control strategy.

In some embodiments, wherein determining that the at least onepre-launch deactivation condition has been met includes determining thata time limit for receiving the brake-on indication has been reached.

In some embodiments, determining that the at least one deactivationcondition has been met includes determining that a temperature oftransmission fluid of the automatic transmission is equal to or greaterthan a predetermined temperature threshold.

In some embodiments, the predefined ramp according to which the torqueof the clutch is increased in the second control strategy is greaterthan a standard ramp according to which the torque of the clutch isincrease in the first control strategy.

In some embodiments, a vehicle comprises: a frame; a driver seatconnected to the frame; a plurality of ground-engaging wheelsoperatively connected to the frame; a powertrain comprising: an internalcombustion engine supported by the frame; a turbocharger operativelyconnected to the engine; and a dual-clutch transmission operativelyconnected to the engine, the dual-clutch transmission comprising: afirst clutch and a second clutch selectively actuated to transmit motionfrom the engine to a first shaft and a second shaft respectively; atleast one first gear mounted to the first shaft; and at least one secondgear mounted to the second shaft, a controller in communication with theengine and the dual-clutch transmission; and an accelerator incommunication with the controller, the controller being configured toperform the method.

In some embodiments, the vehicle is an off-road vehicle; and theaccelerator is an accelerator pedal.

Implementations of the present technology each have at least one of theabove-mentioned object and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presenttechnology that have resulted from attempting to attain theabove-mentioned object may not satisfy this object and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects, and advantages ofimplementations of the present technology will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a perspective view taken from a top, front, left side of anoff-road vehicle;

FIG. 2 is a left side elevation view of the off-road vehicle of FIG. 1 ;

FIG. 3 is a perspective view taken from a top, front, left side of adual-clutch transmission and front propeller shaft of the vehicle ofFIG. 1 ;

FIG. 4 is a perspective view taken from a top, front, left side of thedual-clutch transmission and front propeller shaft of FIG. 3 , with ahousing of the dual-clutch transmission removed;

FIG. 5 is a perspective view taken from a top, rear, left side of thedual-clutch transmission and front propeller shaft of FIG. 4 ;

FIG. 6 is an exploded, perspective view taken from a top, front, leftside of an input damper of the dual-clutch transmission of FIG. 3 ;

FIG. 7 is an exploded, perspective view taken from a top, front, leftside of a dual-clutch of the dual-clutch transmission of FIG. 3 ;

FIG. 8 is a longitudinal cross-sectional view of the dual-clutch and theinput damper of the dual-clutch transmission of FIG. 3 ;

FIG. 9 is a perspective, longitudinal cross-sectional view of the clutchpack drum and the central clutch gear of the dual-clutch of FIG. 7 ;

FIG. 10 is an exploded, perspective view taken from a top, front, leftside of the front clutch hub, front lubrication cover and front pressureplate of the dual-clutch of FIG. 7 ;

FIG. 11 is an exploded, perspective view taken from a rear, left side ofthe front clutch hub, front lubrication cover and front pressure plateof the dual-clutch of FIG. 7 ;

FIG. 12 is an exploded, perspective view taken from a top, front, leftside of the rear pressure plate and rear clutch hub of the dual-clutchof FIG. 7 ;

FIG. 13A is a close-up view of portion 13 of FIG. 8 , with the front andrear pressure plates abutting the central clutch gear of the dual-clutchof FIG. 7 ;

FIG. 13B is a close-up view of portion 13 of FIG. 8 , with the frontpressure plate being moved axially away from the central clutch gear ofthe dual-clutch of FIG. 7 , and with the rear pressure plate abuttingthe central clutch gear;

FIG. 13C is a close-up view of portion 13 of FIG. 8 , with the rearpressure plate being moved axially away from the central clutch gear ofthe dual-clutch of FIG. 7 , and with the front pressure plate abuttingthe central clutch gear;

FIG. 14 is a longitudinal cross-sectional view of a subtransmission ofthe dual-clutch transmission of FIG. 3 ;

FIG. 15 is a block diagram of a controller configured to control thedual-clutch transmission;

FIG. 16 is a flowchart represent a method for controlling a powertrainof the off-road vehicle of FIG. 1 in order to shift between high and lowgear settings without stopping the off-road vehicle;

FIG. 17 is a graph representing engine torque and gear engagements in amain transmission and the subtransmission of the dual-clutchtransmission during execution of the method of FIG. 16 ;

FIG. 18 is a flowchart representing a method for controlling thepowertrain of the off-road vehicle of FIG. 1 in order to reverse a gearshift;

FIG. 19 shows three graphs concurrently representing gear engagement inthe main transmission of the dual-clutch transmission, engine speed, andengine and clutch torques during a shift sequence for upshifting themain transmission;

FIG. 20 shows three graphs concurrently representing gear engagement inthe main transmission of the dual-clutch transmission, engine speed, andengine and clutch torques during a shift sequence for downshifting themain transmission;

FIG. 21 is a flowchart representing a method for accelerating theoff-road vehicle of FIG. 1 from rest; and

FIG. 22 shows two graphs concurrently representing engine speed andclutch torque of the dual-clutch transmission during execution of themethod of FIG. 21 .

DETAILED DESCRIPTION

A dual-clutch transmission (DCT) 100 will be described herein withrespect to a four-wheel side-by-side off-road vehicle 20, but it iscontemplated that the DCT 100 could be used in other types of vehiclessuch as, but not limited to, off-road vehicles having more or less thanfour wheels and/or more or less than two seats. The general features ofthe off-road vehicle 20 will be described with respect to FIGS. 1 and 2.

The vehicle 20 has a frame 22, two front wheels 24 connected to a frontof the frame 22 by front suspension assemblies 26 and two rear wheels 28connected to the frame 22 by rear suspension assemblies 30 such as thosedescribed in U.S. Pat. Serial No. 9,981,519 B2, dated May 29, 2018. Eachfront suspension assembly 26 has a front shock absorber assembly 27including a shock absorber 29 and a spring 31. Each rear suspensionassembly 30 has a rear shock absorber assembly 33 including a shockabsorber 35 and a spring 37. Ground engaging members other than wheels24, 28 are contemplated for the vehicle 20, such as tracks or skis. Inaddition, although four ground engaging members are illustrated in theFigures, the vehicle 20 could include more or less than four groundengaging members. Furthermore, different combinations of ground engagingmembers, such as tracks used in combination with skis, are contemplated.

The frame 22 defines a central cockpit area 42 inside which are disposeda driver seat 44 and a passenger seat 46. In the present implementation,the driver seat 44 is disposed on the left side of the vehicle 20 andthe passenger seat 46 is disposed on the right side of the vehicle 20.However, it is contemplated that the driver seat 44 could be disposed onthe right side of the vehicle 20 and that the passenger seat 46 could bedisposed on the left side of the vehicle 20. As can be seen in FIG. 1 ,the vehicle 20 further has a seat belt 47 for each one of the seats 44,46. A steering wheel 48 is disposed in front of the driver seat 44. Thesteering wheel 48 is used to turn the front wheels 24 to steer thevehicle 20. Various displays and gauges 50 are disposed in front of thesteering wheel 48 to provide information to the driver regarding theoperating conditions of the vehicle 20. Examples of displays and gauges50 include, but are not limited to, a speedometer, a tachometer, a fuelgauge, a transmission position display, and an oil temperature gauge.

Referring to FIG. 2 , a powertrain of the vehicle 20 includes aninternal combustion engine 52 (schematically shown in FIGS. 2 and 3 )connected to the frame 22 in a rear portion of the vehicle 20. Theengine 52 has a crankshaft 53 (schematically shown in FIG. 3 ) that isconnected to the DCT 100 disposed behind the engine 52 (bothschematically shown in FIG. 2 ). The vehicle 20 has an accelerator 45(FIG. 2 ) in the central cockpit area 42 for use by the driver tocontrol a position of a throttle valve (not shown) that regulates airintake into the engine 52, thereby controlling acceleration of thevehicle 20. In this embodiment, the accelerator 45 is an acceleratorpedal for control with the driver’s foot. It is contemplated that theaccelerator 45 could be any other suitable type of accelerator in otherembodiments (e.g., a lever at a handlebar). In this embodiment, asillustrated schematically in FIG. 3 , the vehicle 10 has a turbocharger57 operatively connected to the engine 52. The turbocharger 57 is drivenby rotation of the crankshaft 53 to provide boost pressure to the engine52 thereby increasing a power output of the engine 52. The DCT 100includes a subtransmission 700 (FIGS. 4, 5 and 14 ) operativelyconnected to a driveline 54 (schematically shown in FIG. 2 ) of thevehicle 20 for operatively connecting the front and rear wheels 24, 28to the engine 52 in order to propel the vehicle 20. A gear shifter 56(FIG. 2 ) located between the seats 44, 46 operates the DCT 100 and thesubtransmission 700 of the vehicle 20, and enables the driver to selectone of a plurality of gear configurations for operation of the vehicle20 (e.g., high or low gear settings, and a parking setting). It iscontemplated that paddle shifters (not shown) could be mounted to thesteering wheel 48 for enabling the driver to select a gear for operationof the vehicle 20. In the illustrated implementation of the vehicle 20,the gear configurations made available by the DCT 100 include a reversegear, and forward first, second, third, fourth, fifth, sixth and seventhgear. The gear configurations made available by the subtransmission 700include park, neutral, high forward gears, and low forward gears. Thus,the DCT 100 and the subtransmission 700 enable fourteen differentforward-going gear configurations and two different reverse gearconfigurations. It is contemplated that the sequence and/or number ofgear configurations could be different than as shown herein in otherimplementations.

A driving mode selector button 58 (FIG. 2 ) also enables the driver toselect 2×4 or 4×4 operation of the vehicle 20. More particularly, thedriveline 54 includes a front propeller shaft 60 which extendshorizontally to the left of the engine 52 towards a front differentialassembly 62 (schematically shown in FIG. 2 ). The front differentialassembly 62 is operatively connected to the front wheels 24 via frontwheel axle assemblies (not shown). The front differential assembly 62includes an electronic selector 64 (also schematically shown in FIG. 2 )operatively connected to the driving mode selector button 58. Theelectronic selector 64 allows to selectively connect the front propellershaft 60 to the front wheel axle assemblies to enable 4×4 driving modeof the vehicle 20, or to selectively disconnect the front propellershaft 60 from the front wheel axle assemblies to enable 2×4 driving modeof the vehicle 20 (i.e. with only the rear wheels 28 propelling thevehicle 20).

The vehicle 20 further includes other components such as brakes, aradiator, headlights, and the like. As it is believed that thesecomponents would be readily recognized by one of ordinary skill in theart, further explanation and description of these components will not beprovided herein.

Turning now to FIGS. 3 to 14 , the DCT 100 will be described in moredetail. The DCT 100 includes a housing 102 that is separate from theinternal combustion engine 52. The housing 102 is flanged to a rear faceof the internal combustion engine 52. In addition, the housing 102 has adedicated hydraulic and lubrication oil circuit, separated from that ofthe engine 52. A transmission fluid pump 104 (schematically shown inFIG. 3 ) is received inside the housing 102. The transmission fluid pump104 is adapted to selectively pump transmission fluid, such as oil-basedfluids. Again, in the present implementation, the transmission fluidpump 104 is separated from any other pump(s) the engine 52 may have.

Referring to FIGS. 4 to 6 , the DCT 100 includes an input damper 120adapted to reduce the torque variations from the crankshaft 53 to theDCT 100. The input damper 120 has a hollow shaft 122 defining splines124 for connection to the crankshaft 53 (as can be understood from FIG.3 ). The hollow shaft 122 has a front end 126 and a rear end 128 definedconsistently with the forward travel direction of the vehicle 20 (FIGS.6 and 8 ). The hollow shaft 122 also defines an input damper axis 130about which the hollow shaft 122 rotates. An input member 140 isslidably engaged to the hollow shaft 122 and positioned between thefront and rear ends 126, 128. The input member 140 has splines 141complementary to splines 124, and the input member 140 can slide axiallyalong the input damper axis 130 between the front and rear ends 126,128. The input member 140 defines three recesses 142 angularly displacedby about 120 degrees relative to the input damper axis 130. A discspring assembly 150 is connected to the hollow shaft 122 and extendsbetween the front and rear ends 126, 128. The disc spring assembly 150abuts a shoulder 152 of the hollow shaft 122 and biases the input member140 axially along the input damper axis 130 towards the rear end 128 ofthe hollow shaft 122. An output member 160 is disposed over the hollowshaft 122 and positioned between the input member 140 and the rear end128 of the hollow shaft 122. The output member 160 is supported bybearings 162 disposed between the output member 160 and a connector 164disposed adjacent the rear end 128 of the hollow shaft 122. Theconnector 164 retains the output member 160 on the hollow shaft 122. Theoutput member 160 defines three cams 166 also angularly displaced byabout 120 degrees relative to the input damper axis 130 (FIG. 6 ). Thethree cams 166 are structured and configured for engaging thecorresponding three recesses 142 of the input member 140 when the inputmember 140 is biased towards the rear end 128 of the hollow shaft 122.An output gear 170 is connected to the output member 160, and alsorotates about the input damper axis 130. The output gear 170 has aplurality of teeth 172. A pump gear 180 is connected to the output gear170 via three fasteners 182, and extends between the output gear 170 andthe disc spring assembly 150. The pump gear 180 also rotates about theinput damper axis 130. The pump gear 180 is adapted to drive thetransmission fluid pump 104 (FIG. 2 ). An auxiliary output gear 190 isconnected to the output gear 170 via a ring 191 having coil springassemblies 192. The auxiliary output gear 190 is biased by the coilspring assemblies 192 and has a plurality of teeth 194. In the presentimplementation, the number of teeth 172 of the output gear 170 matchesthe number of teeth 194 of the auxiliary output gear 190. The coilspring assemblies 192 permits angular displacements of the auxiliaryoutput gear 190 about the input damper axis 130 relative to the outputgear 170. The auxiliary output gear 190 provides preload on the teeth172 of the output gear 170 and reduces backlash that can occur betweenthe output gear 170 and a central clutch gear 200 described below.

Referring to FIGS. 4 to 8 , the DCT 100 includes a dual-clutch 202having first and second clutches 204 a, 204 b. Before describing indetails the first and second clutches 204 a, 204 b, components of thedual clutch 202 will be described. The dual clutch 202 includes a clutchpack drum 220 that is adapted to rotate inside the housing 102, and thecentral clutch gear 200 is connected to the clutch pack drum 220 viafasteners 221 (FIGS. 7 and 9 ). The central clutch gear 200 has teeth212 adapted to mesh with the teeth 172, 194 of the output gear 170 andthe auxiliary output gear 190. The central clutch gear 200 is thusoperatively connected to the crankshaft 53 of the internal combustionengine 52 via the input damper 120. It is to be noted that having theinput damper 120 located outside the clutch pack drum 220 offers moreflexibility to package the DCT 100 in the rear portion of the frame 22of the vehicle 20 supporting the engine 52 and the DCT 100. Thus, havingthe input damper 120 located outside the clutch pack drum 220 improvesthe overall packaging of the DCT 100 in the rear portion of the vehicle20. Moreover, having the input damper 120 located outside the clutchpack drum 220 allows for a greater angle of relative rotation betweenthe input member 140 and the output member 160 compared to an inputdamper that would be integrated in the clutch pack drum 220. The greaterangle of relative rotation between the input member 140 and the outputmember 160 improves the damping provided by the input damper 120.

Referring to FIGS. 7 and 9 , the central clutch gear 200 has a frontface 212 a and a rear face 212 b. The central clutch gear 200 defines aclutch gear plane 214 and a clutch gear rotation axis 216 normal to theclutch gear plane 214 (FIG. 8 ). It is to be appreciated that the clutchgear rotation axis 216 is parallel to the input damper axis 130, andextends above and to the right of the input damper axis 130 (FIG. 4 ).

Referring to FIGS. 7 to 9 , the clutch pack drum 220 includes a frontclutch pack basket 222 a disposed in front of the central clutch gear200, and a rear clutch pack basket 222 b disposed behind the centralclutch gear 200. The front and rear clutch pack baskets 222 a, 222 b areinterconnected using the fasteners 221 extending through the centralclutch gear 200. The front and rear clutch pack baskets 222 a, 222 b areidentical. In some implementations, the front and rear clutch packbaskets 222 a, 222 b are symmetrical about the clutch gear plane 214.The front and rear clutch pack baskets 222 a, 222 b could be structuredotherwise in other implementations. Having the front and rear clutchpack baskets 222 a, 222 b identical, or symmetrical about the clutchgear plane 214, assists in reducing the manufacturing costs of the DCT100. The front and rear clutch pack baskets 222 a, 222 b each have acylindrical wall 226 defining splines 228 and a plurality of holes 230.

Turning now to FIGS. 7 to 13C, the first clutch 204 a will be describedin details first. The operation of the first and second clutches 204 a,204 b, and the flow of fluid through the DCT 100 will be describedfurther below. A front clutch pack 240 a is received in the clutch packbasket 222 a and is disposed in front of the central clutch gear 200.The clutch pack 240 a includes a plurality of clutch plates 242 havingteeth 244 extending away from the clutch gear rotation axis 216 andengaging the splines 228 of the clutch pack basket 222 a for rotatingwith the clutch pack drum 220 (FIG. 13A). The clutch plates 242 aremovable axially in a direction 246 (see double arrow 246 in FIGS. 13A to13C) defined by the clutch gear rotation axis 216. The clutch plates 242have disc surfaces including relatively low friction material. The frontclutch pack 240 a further includes a plurality of clutch disks 250disposed alternatingly with the clutch plates 242 in the direction 246(FIG. 13A). The clutch disks 250 have disc surfaces including arelatively high friction material. The clutch disks 250 have teeth 254extending towards the clutch gear rotation axis 216. The clutch disks250 are also movable axially in the direction 246 defined by the clutchgear rotation axis 216. As will become apparent from the descriptionbelow, when the clutch disks 250 are selectively engaged by the clutchplates 242, the clutch disks 250 rotate with the clutch pack drum 220.

Referring to FIGS. 7, 10 and 11 , a front clutch hub 260 a is receivedin the clutch pack 240 a and is disposed in front of the central clutchgear 200. The clutch hub 260 a defines splines 262 structured to engagewith the teeth 254 of the clutch disks 250 of the clutch pack 240 a. Theclutch disks 250 are movable axially relative to the clutch hub 260 a inthe direction 246 defined by the clutch gear rotation axis 216 as theteeth 254 slide axially in the splines 262. When the clutch disks 250are selectively engaged by the clutch plates 242, the clutch hub 260 arotates with the clutch pack drum 220. The clutch hub 260 a has threearms 264 connecting a rim portion 266 of the clutch hub 260 a (definingthe splines 262) to a central portion 268 of the clutch hub 260 a. Holes270 are defined in each of the arms 264 for receiving fasteners 272(FIG. 13A). The central portion 268 defines splines 274. Referring toFIGS. 10, 11 and 13A, a plurality of bores 280 are defined in thecentral portion 268, in the arms 264 and in the rim portion 266. Thebores 280 are adapted for allowing flow of fluid therethrough, as willbecome apparent from the following description.

Referring to FIGS. 10 and 11 , a lubrication cover 300 a is alsoreceived in the clutch pack 240 a. The lubrication cover 300 a isdisposed in front of the central clutch gear 200 and behind the frontclutch hub 260 a. The lubrication cover 300 a defines a plurality ofapertures 302 on a rim portion 304 thereof. Three threaded holes 306 aredefined in the lubrication cover 300 a for receiving the fasteners 272.When the fasteners 272 extend through the holes 270 of the clutch hub260 a and are engaged in the threaded holes 306 of the lubrication cover300 a, the lubrication cover 300 a and the clutch hub 260 a areinterconnected. Passages 310 are defined in the lubrication cover 300 aand extend around each one of the threaded holes 306. The passages 310are adapted for allowing flow of fluid therethrough, as will becomeapparent from the following description.

Referring to FIGS. 7, 10, 11 and 13A, the DCT 100 further includes apressure plate 320 a disposed in front of the central clutch gear 200.The pressure plate 320 a is disposed between the central clutch gear 200and the lubrication cover 300 a. A ring 322 a is connected to thecentral clutch gear 200, and coil spring assemblies 324 a interconnectthe pressure plate 320 a to the central clutch gear 200. The pressureplate 320 a rotates with the central clutch gear 200, and is movableaxially in the direction 246 upon compression and extension of the coilspring assemblies 324 a. The pressure plate 320 a has a front face 332 a(FIG. 10 ) including a rim portion 334 a. The rim portion 334 a of thepressure plate 320 a is structured to selectively engage the clutchplate 242 that is closest to the central clutch gear 200. The pressureplate 320 a further has a rear face 342 a (FIG. 11 ) where six pads 344project therefrom. The pads 344 are structured for abutting the frontface 212 a of the central clutch gear 200 and to leave a spacing betweenthe front face 212 a of the central clutch gear 200 and the rear face342 a of the pressure plate 320 a (the spacing is shown in FIG. 13A).Referring to FIGS. 13A to 13C, a chamber 350 a is defined between thefront face 212 a of the central clutch gear 200 and the rear face 342 aof the pressure plate 320 a. Seals 352 are disposed between the pressureplate 320 a and the central clutch gear 200 to prevent fluid fromescaping the chamber 350 a through the regions where the seals 352extend. The pressure plate 320 a further defines a pressure platepassage 360 a extending between the front face 332 a and the rear face342 a. More particularly, the pressure plate passage 360 a starts on therear face 342 a from one of the pads 344 (FIG. 11 ). The pressure platepassage 360 a is adapted for allowing flow of fluid therethrough, aswill become apparent from the following description.

Referring to FIGS. 4, 8, and 13A, a shaft 400 a is connected to thefront clutch hub 260 a via teeth (not shown) engaging the splines 274 ofcentral portion 268. The shaft 400 a is coaxial with the clutch gearrotation axis 216. The shaft 400 a defines three passages 410, 412 (FIG.13A), and 414 (FIG. 8 ) adapted for flowing fluid therethrough. Amanifold 420 (FIG. 8 ) is connected to the front portion of the shaft400 a. The manifold 420 fluidly connects the transmission fluid pump 104to the passages 410, 412, 414. Three plugs (not shown) seal the ends ofthe passages 410, 412, 414 defined in the front portion of the shaft 400a (FIG. 4 ). Referring to FIGS. 4, 5 and 14 , a plurality oftransmission gears 600 are operatively connected to the shaft 400 a. Thetransmission gears 600 include the gears corresponding to the first gear601, third gear 603, fifth gear 605, and seventh gear 607 of the DCT100. The transmission gears 600 are all disposed behind the centralclutch gear 200.

Arrows show the flow of fluid through the dual-clutch 202 in FIGS. 10,11, 13A and 13B when the dual-clutch 202 rotates. When fluid isselectively supplied in the passage 410 from the transmission fluid pump104, fluid flows through the shaft 400 a in the passage 410 (FIG. 13A),through passages 430 a defined in the central clutch gear 200 (FIGS. 9and 13A) and into the chamber 350 a. Since the pads 344 abut the frontface 212 a of the central clutch gear 200, fluid flows through thespacing between the pressure plate 320 a and the central clutch gear200, and fills the chamber 350 a. The pads 344 are thus structured forselectively allowing flow of fluid from the passage 410 to the chamber350 a. When the fluid is selectively supplied with sufficient pressureby the transmission fluid pump 104, the pressurized fluid in the chamber350 a overcomes the biasing force of the coil spring assemblies 324 aand moves the pressure plate 320 a axially away from the central clutchgear 200 (i.e. forward of the central clutch gear 200), as shown betweenFIGS. 13A and 13B. The pressure plate 320 a selectively squeezes theclutch plates 242 and the clutch disks 250 together for engaging theclutch plates 242 with the clutch disks 250. The front clutch hub 260 aand the lubrication cover 300 a are thus rotatable with the clutch packdrum 220 and the central clutch gear 200, and the shaft 400 a drives thetransmission gears 600 corresponding to the first gear 601, third gear603, fifth gear 605 and seventh gear 607 of the DCT 100.

Referring to FIG. 13B, as some of the fluid escapes the chamber 350 athrough the pressure plate passage 360 a (as shown by the arrows in FIG.13B), fluid flows in the front clutch pack 240 a and lubricates andcools the clutch plates 242, the clutch disks 250, and the clutch packbasket 222 a, as shown by arrows in FIG. 13B. Fluid flows through theholes 230 of the clutch pack basket 222 a, is collected in the housing102 and is returned to the transmission fluid pump 104 for recirculationin the DCT 100. It is thus to be understood that in order for thepressure plate 320 a to selectively squeeze the clutch pack 240 a,pressurized fluid is continuously supplied in the chamber 350 a by thetransmission fluid pump 104.

Referring to FIG. 13A, when fluid is selectively supplied in the passage414 (FIG. 8 ) and as the first clutch 204 a rotates, fluid flows throughthe shaft 400 a, through the bores 280 defined in the central portion268, in the arms 264 and in the rim portion 266 of the front clutch hub260 a, and through the aperture 302 and passages 310 defined in thelubrication cover 300 a, and on to the front clutch pack 240 a, as shownby arrows in FIG. 13A. The fluid flowing through the passage 414provides additional lubrication and cooling to the clutch plates 242,the clutch disks 250, and the clutch pack basket 222 a of the firstclutch 204 a. Since the first clutch 204 a is operatively connected tothe transmission gear 600 corresponding to the first gear 601 of the DCT100, which can have a heavy usage, for example, when the vehicle 20launches repetitively, additional lubrication and cooling to the firstclutch 204 a provided by fluid flowing through the passage 414 and thebore 280 is advantageous under certain conditions.

Referring to FIGS. 7, 8 and 12 , the second clutch 204 b will now bedescribed. A rear clutch pack 240 b is received in the clutch packbasket 222 b and is disposed behind the central clutch gear 200. Therear clutch pack 240 b also includes a plurality of clutch plates 242having teeth 244 extending away from the clutch gear rotation axis 216and engaging the splines 228 of the clutch pack basket 222 b forrotating with the clutch pack drum 220 (FIGS. 13A to 13C). In thepresent implementations, the front and rear clutch packs 240 a, 240 bare identical, but they could be structured otherwise in otherimplementations. This feature assists in reducing the manufacturingcosts of the DCT 100. The clutch plates 242 have disc surfaces includinga relatively low friction material. The rear clutch pack 240 b furtherincludes a plurality of clutch disks 250 disposed alternatingly with theclutch plates 242 in the direction 246 (FIG. 13A). The clutch disks 250have disc surfaces including a relatively high friction material. Theclutch disks 250 have teeth 254 extending towards the clutch gearrotation axis 216 (FIGS. 13A to 13C). The clutch disks 250 are alsomovable axially in the direction 246 defined by the clutch gear rotationaxis 216.

Referring to FIGS. 7 and 12 , a rear clutch hub 260 b is received in theclutch pack 240 b and is disposed behind the central clutch gear 200.The clutch hub 260 b also defines splines 262 structured to engage withthe teeth 254 of the clutch disks 250 of the clutch pack 240 b. Theclutch disks 250 are movable axially relative to the clutch hub 260 b inthe direction 246 (FIGS. 13A to 13C). When the clutch disks 250 areselectively engaged by the clutch plates 242, the clutch hub 260 brotates with the clutch pack drum 220. The clutch hub 260 b has eightarms 264 connecting a rim portion 266 of the clutch hub 260 b to thecentral portion 268 of the clutch hub 260 b. The central portion 268defines splines 274. Referring to FIG. 12 , a plurality of bores 280 arealso defined in the central portion 268, in the arms 264 and in the rimportion 266 of the clutch hub 260 b. The bores 280 are adapted forallowing flow of fluid therethrough, as will become apparent from thefollowing description.

Referring to FIGS. 7 and 12 , the DCT 100 further includes a pressureplate 320 b disposed behind the central clutch gear 200. The pressureplate 320 b is disposed between the central clutch gear 200 and theclutch hub 260 b. A ring 322 b (FIG. 7 ) is connected to the centralclutch gear 200, and coil spring assemblies 324 b interconnect thepressure plate 320 b to the central clutch gear 200. It is to be notedthat the rings 322 a, 322 b are identical, and that the springassemblies 324 a, 324 b are identical. These features assist in reducingthe manufacturing costs of the DCT 100. The pressure plate 320 b rotateswith the central clutch gear 200, and is movable axially in thedirection 246 upon compression and extension of the coil springassemblies 324 b. The pressure plate 320 b has a rear face 332 bincluding a rim portion 334 b. The rim portion 334 b of the pressureplate 320 a is structured to selectively engage the clutch plate 242 ofthe rear clutch pack 240 b that is closest to the central clutch gear200. The pressure plate 320 b further has a front face 342 b where sixpads 344 project therefrom. The pads 344 are structured for abutting therear face 212 b of the central clutch gear 200 and to leave a spacingdefined between the rear face 212 b of the central clutch gear 200 andthe front face 342 b of the pressure plate 320 b (FIG. 13A). A chamber350 b is defined between the rear face 212 b of the central clutch gear200 and the front face 342 b of the pressure plate 320 b. Seals 352 arealso disposed between the pressure plate 320 b and the central clutchgear 200 to prevent fluid from escaping the chamber 350 b through theregions where the seals 352 extend. The pressure plate 320 b furtherdefines a pressure plate passage 360 b (FIG. 12 ) extending between therear face 332 b and the front face 342 b. More particularly, thepressure plate passage 360 b starts on the front face 342 b from one ofthe pads 344. The pressure plate passage 360 b is adapted for allowingflow of fluid therethrough, as will become apparent from the followingdescription.

It is to be appreciated that in the illustrated implementation, thepressure plates 320 a, 320 b are identical. In some implementations, thepressure plates 320 a, 320 b are symmetrical about the clutch gear plane214. These features assist in reducing the manufacturing costs of theDCT 100. Furthermore, there is no component similar to the lubricationcover 300 a in the second clutch 204 b.

Referring to FIGS. 13A to 13C, arrows show the flow of fluid through thedual-clutch 202 when the dual-clutch 202 rotates and fluid isselectively supplied in the passages 410, 412, 414. When fluid isselectively supplied in the passage 412 of the shaft 400 a, fluid flowsthrough the shaft 400 a in the passage 412 (FIGS. 13A and 13C), throughpassages 430 b defined in the central clutch gear 200 (FIG. 9 ) and intothe chamber 350 b. Since the pads 344 abut the rear face 212 b of thecentral clutch gear 200, fluid flows through the spacing between thepressure plate 320 b and the central clutch gear 200, and fills thechamber 350 b. The pads 344 are thus structured for selectively allowingflow of fluid from the passage 412 to the chamber 350 b. When the fluidis selectively supplied with sufficient pressure, the pressurized fluidin the chamber 350 b overcomes the biasing force of the coil springassemblies 324 b and moves the pressure plate 320 b axially away fromthe central clutch gear 200 (i.e. rearward of the central clutch gear200), as shown between FIGS. 13A and 13C. The pressure plate 320 bselectively squeezes the clutch plates 242 and the clutch disks 250together for engaging the clutch plates 242 with the clutch disks 250.The rear clutch hub 260 b is thus rotatable with the clutch pack drum220 and the central clutch gear 200. As some of the fluid escapes thechamber 350 b through the pressure plate passage 360 b, fluid flows inthe rear clutch pack 240 b and lubricates and cools the clutch plates242, the clutch disks 250, and the clutch pack basket 222 b, as shown byarrows in FIG. 13C. Fluid flows through the holes 230 of the clutch packbasket 222 b, is collected in the housing 102 and is returned to thetransmission fluid pump 104 for recirculation in the DCT 100. It is thusto be understood that in order for the pressure plate 320 b toselectively squeeze the clutch pack 240 b, pressurized fluid iscontinuously supplied by the transmission fluid pump 104.

Furthermore, it is to be noted that in the DCT 100 of the presenttechnology, having the central clutch gear 200 between the pressureplates 320 a, 320 b, and thus the chambers 350 a, 350 b on either sideof the central clutch gear 200, assists in distributing the forces moreevenly in the clutch pack drum 220. This feature also assists inreducing the rotating masses in the clutch pack drum 220.

Referring to FIG. 8 , a hollow shaft 400 b is connected to the rearclutch hub 260 b via the splines 274 defined in the central portion 268thereof. The shaft 400 a extends through the shaft 400 b. Anotherplurality of transmission gears 600 are operatively connected to theshaft 400 b. Referring to FIG. 5 , the transmission gears 600 includethe gears corresponding to the second gear 602, fourth gear 604 andsixth gear 606 of the DCT 100, and the transmission gears 600 are alsodisposed behind the central clutch gear 200.

Referring back to FIGS. 4 and 5 , the DCT 100 further includes alayshaft 610 having additional transmission gears 601′, 603′, 605′, 607′operatively connected thereto. Each of the transmission gears 601′,603′, 605′, 607′ on the layshaft 610 is selected to have a gear ratiowith the corresponding transmission gear 601, 603, 605, 607 tocorrespond to the first, third, fifth and seventh gear of the DCT 100.The DCT 100 further includes another layshaft 620 having additionaltransmission gears (not shown) operatively connected thereto. Each ofthe transmission gears on the layshaft 620 is selected to have a gearratio with the corresponding transmission gear 602, 604, 606 tocorrespond to the second, fourth and sixth gear of the DCT 100. Thelayshaft 620 further includes the transmission gear 608 corresponding toa reverse gear of the DCT 100. An output gear 630 is operativelyconnected to each of the layshafts 610, 620 to operatively connect thetransmission gears 600 to the subtransmission 700. The transmissiongears 600 mounted to the shafts 400 a, 400 b and the transmission gearsmounted to the layshafts 610, 620 define a main transmission 615 of theDCT 100.

The DCT 100 further includes synchronizers, shift actuators and shiftforks adapted to preselect an odd transmission gear on the shaft 400 awhile the vehicle 20 is being driven in an even transmission gear on theshaft 400 b (and vice versa), and thus enable the driver to operatetransmission gear changes when the driver operates the gear shifter 56.

Referring now to FIGS. 4, 5 and 14 , the subtransmission 700 will bedescribed in more details. The subtransmission 700 has an input shaft702. An input gear 704 is operatively connected to the input shaft 702via an output damper 710. The input gear 704 is selectively driven bythe output gear 630 of the layshaft 610, or by the output gear 630 ofthe layshaft 620, depending on the transmission gear that is selected.As such, the subtransmission 700 is operatively connected to the maintransmission 615 via the input gear 704 and the output gears 630. Theoutput damper 710 is operatively connected between the input gear 704and the input shat 702. The output damper 710 has components similar tothe input damper 120, and can reduce backlash that can occur between thedriveline 54 of the vehicle 20 and the DCT 100. A parking lock gear 720is operatively connected to the input shaft 702, and is adapted to lockthe subtransmission 700, and thus the vehicle 20, when selected. Thesubtransmission 700 further includes a high transmission gear 730 and alow transmission gear 732 operatively connected to the input shaft 702.The high transmission gear 730 and the low transmission gear 732 areselectively engageable to place the subtransmission 700 in a “high gearsetting” and a “low gear setting” respectively.

The subtransmission 700 further includes an output shaft 740 configuredfor operative connection to the driveline 54 of the vehicle 20 (as shownby arrow 54 in FIGS. 4, 5 and 14 ). The output shaft 740 includes a hightransmission gear 730′ and a low transmission gear 732′ operativelyconnected thereto. When the subtransmission 700 is in the high gearsetting (i.e. when the high transmission gear 730 drives the hightransmission gear 730′), a first gear ratio is defined between the inputshaft 702 and the output shaft 740. When the subtransmission 700 is inthe low gear setting (i.e. when the low transmission gear 732 drives thelow transmission gear 732′), a second gear ratio is defined between theinput shaft 702 and the output shaft 740. The first gear ratio (i.e.high gear ratio) is smaller than the second gear ratio (i.e. low gearratio). The driver can thus select in which mode the subtransmission 700is to be configured, i.e. between high gear ratio and low gear ratio,depending on the terrain on which the vehicle 20 travels, for example.

The output shaft 740 further has a bevel gear 750 defined in the rearportion thereof. The bevel gear 750 is adapted to operatively connect toa rear transaxle 751 of the vehicle 20 for driving the rear wheels 28(as indicated by arrows 28 on FIG. 4 ). A front propeller shaft gear 752is operatively connected to the output shaft 740, and is adapted toengage with a front propeller shaft gear 752′ operatively connected tothe front propeller shaft 60. As mentioned above, the front propellershaft 60 selectively drives the front wheels 24 when the driver selects4×4 operation of the vehicle 20.

Different methods for controlling the powertrain of the vehicle 20 willnow be described with reference to FIGS. 16 to 22 . According to variousembodiments, a controller 500 (illustrated schematically in FIG. 3 ) isin communication with the DCT 100 to control its operation. For example,the shifting of the gears of the DCT 100, including the gears 600, iscontrolled by the controller 500, notably by controlling the actuationof the first and second clutches 204 a, 204 b and controlling the shiftactuators. As shown in FIG. 15 , the controller 500 has a processor unit525 for carrying out executable code, and a non-transitory memory unit535 that stores the executable code in a non-transitory medium (notshown) included in the memory unit 535. The processor unit 525 includesone or more processors for performing processing operations thatimplement functionality of the controller 500. The processor unit 525may be a general-purpose processor or may be a specific-purposeprocessor comprising one or more preprogrammed hardware or firmwareelements (e.g., application-specific integrated circuits (ASICs),electrically erasable programmable read-only memories (EEPROMs), etc.)or other related elements. The non-transitory medium of the memory unit535 may be a semiconductor memory (e.g., read-only memory (ROM) and/orrandom-access memory (RAM)), a magnetic storage medium, an opticalstorage medium, and/or any other suitable type of memory. While thecontroller 500 is represented as being one control unit in thisimplementation, it is understood that the controller 500 could compriseseparate control units for controlling components separately and that atleast some of these control units could communicate with each other.Moreover, in some embodiments, the controller 500 could be incommunication with an electronic control unit (ECU) of the vehicle 20that controls operation of the engine 52. In some embodiments, thecontroller 500 could be the ECU of the vehicle 20.

During operation, the driver of the vehicle 20 may face situations inwhich it is beneficial to shift the DCT 100 from operating in the highgear setting to the low gear setting or vice-versa. As described above,the high gear setting is associated with operating the DCT 100 such asto drive the output shaft 740 in part by the high transmission gear 730driving the high transmission gear 730′, while the low gear setting isassociated with operating the DCT 100 such as to drive the output shaft740 with the low transmission gear 732 driving the low transmission gear732′. For example, when the vehicle 20 is traversing a rocky terrain(i.e., while rock crawling), it may be beneficial for the user to shiftthe DCT 100 such as to operate in the low gear setting to maximize atorque output at the output shaft 740. In a conventional vehicleequipped with a subtransmission that allows for shifting into high andlow gear settings, this requires the driver to first stop the vehicle tobe in a stand-still state (i.e., at rest) and then shifting fromoperating in the high gear setting to the low gear setting. This may bebothersome to the driver as it could require stopping the vehicle manytimes to shift the DCT back and forth from the high gear setting to thelow gear setting as needed. Thus with particular reference to FIGS. 16and 17 , a method 800 for controlling the powertrain of the vehicle 20in order to shift between the high gear setting and the low gear settingwithout stopping the vehicle 20 will be described herein.

At step 810, the method 800 begins with the vehicle 20 driving with theDCT 100 operating in the high gear setting or the low gear setting. Thatis, either the high transmission gear 730 or the low transmission gear732 is drivingly engaged to the input shaft 702 to drive the outputshaft 740. The driver then operates the gear shifter 56 to shift the DCT100 to be in the other one of the high gear setting or the low gearsetting. That is, if at step 810 the DCT 100 is in the high gearsetting, the driver operates the gear shifter 56 to shift the DCT 100 tobe in the low gear setting. In that case, the method 800 proceeds tostep 820 a where a low gear shift request is generated and transmittedto the controller 500 requesting the low transmission gear 732 to beengaged on the input shaft 702 in order to drive the output shaft 740with the low transmission gear 732. On the other hand, if at step 810the DCT 100 is in the low gear setting, the driver operates the gearshifter 56 to shift the DCT 100 be in the high gear setting. In thatcase, the method 800 proceeds to step 820 b where a high gear shiftrequest is generated and transmitted to the controller 500 requestingthe high transmission gear 730 to be engaged on the input shaft 702 inorder to drive the output shaft 740 with the high transmission gear 730.

In this embodiment, from step 820 a, the method 800 proceeds to step 830whereby the controller 500 validates if an operating speed associatedwith the vehicle 20 is adequate for shifting to the low gear setting. Inthe present embodiment, the operating speed is determined based at leastin part on the rotational speed of the transmission output shaft. Morespecifically, a sensor (not shown) detects the speed of the frontpropeller shaft gear 752′. It is contemplated that the operating speedcould be determined based on the vehicle speed, but in such cases theexact, correct tire size would need to be received by the controller 500(for example by entering the tire size in the vehicle setup by theuser). In particular, at step 830, the controller 500 compares theoperating speed associated with the vehicle 20 to a predetermined speedV_(H1). In this embodiment, the operating speed associated with thevehicle 20 compared at step 830 is a speed of the vehicle 20, and thepredetermined speed V_(H1) is a predetermined vehicle speed V_(H1). Inresponse to the speed of the vehicle 20 being greater than thepredetermined vehicle speed V_(H1), the controller 500 denies the lowgear shift request generated at step 820 a. Notably, this helps protectthe DCT 100 and/or the engine 52 as shifting into the low gear settingwhile the vehicle 20 is travelling at high speeds could potentiallycause damage to the DCT 100 or the engine 52. As shown in FIG. 15 , inthis embodiment, a speed sensor 545 senses the speed of the vehicle 20and is in communication with the controller 500 to transmit electronicsignals thereto that are indicative of the speed of the vehicle 20.

In this embodiment, after denying the low gear shift request, the method800 proceeds to step 840 whereby the controller 500 causes a displayelement 805 (FIG. 15 ) visible to the driver to display an indication tothe driver indicative of the denial of the low gear shift request. Inthis embodiment, as shown in FIG. 2 , the display element 805 isprovided on a dashboard of the vehicle 20. For instance, the displayelement 805 may be an icon on a display screen disposed on the dashboardof the vehicle 20. From the step 840, the method 800 then proceeds backto step 810 as the vehicle 20 continues to be driven with the DCT 100operating in the high gear setting.

If instead, at step 830, the controller 500 determines that the speed ofthe vehicle 20 is less than or equal to the predetermined vehicle speedV_(H1), the method 800 proceeds to step 850 in order to fulfill theshift request.

It is contemplated that, in other embodiments, at step 830, theoperating speed associated with the vehicle 20 could be a speed of theDCT 100 (e.g., of the central clutch gear 200 or another part of the DCT100) and the predetermined speed V_(H1) to which it is compared is acorresponding predetermined speed of the DCT 100.

As shown in FIG. 16 , in this embodiment, from step 820 b, the method800 proceeds to step 832 whereby the controller 500 validates if anoperating speed associated with the vehicle 20 and a torque output ofthe engine 52 are adequate for shifting to the high gear setting. Inparticular, at step 832, the controller 500 compares the operating speedassociated with the vehicle 20 and the torque output of the engine 52 toa predetermined map of values of the speed V_(H2) and a correspondingpredetermined engine torque T_(E), the predetermined engine torque T_(E)generally increasing as the speed V_(H2) increases In this embodiment,the operating speed associated with the vehicle 20 is the speed of thevehicle 20, and the speed V_(H2) is a vehicle speed V_(H2). Thepredetermined speed V_(H2) could be different from the predeterminedspeed V_(H1) of step 830. In response to the torque output of the engine52 being greater than the predetermined engine torque T_(E)corresponding to the speed V_(H2) the controller 500 denies the highgear shift request generated at step 820 b. Notably, this helps protectthe DCT 100 and/or the engine 52 as shifting into the high gear settingwhile the vehicle 20 is travelling at low speeds and at high enginetorque could potentially cause stalling of the engine 52 or even damageto the DCT 100 or the engine 52. For example, this could be the casewhen the vehicle 20 is climbing up a slope. It is contemplated that, inother embodiments, at step 832, the operating speed associated with thevehicle 20 could be a speed of the DCT 100 (e.g., of the central clutchgear 200 or another part of the DCT 100) and the speed V_(H2) value mapto which it is compared is a corresponding value map of the speed of theDCT 100.

In this embodiment, after denying the high gear shift request, themethod 800 proceeds to step 840 whereby the controller 500 causes thedisplay element 805 (FIG. 15 ) to display an indication to the driverindicative of the denial of the high gear shift request. From the step840, the method 800 then proceeds back to step 810 as the vehicle 20continues to be driven with the DCT 100 operating in the low gearsetting.

If instead, at step 832, the controller 500 determines that either thespeed of the vehicle 20 is greater than or equal to the predeterminedvehicle speed V_(H2), or that the torque output of the engine 52 is lessthan or equal to the predetermined engine torque T_(E), the method 800proceeds to step 850 in order to fulfill the shift request.

At step 850, in response to either the low gear shift request or thehigh gear shift request, the torque output of the engine 52 is reduced.This corresponds to time t1 in the graph of FIG. 17 which exemplifiesthe variation of the torque output of the engine 52 as well as theengaged gears of the main transmission 615 and the subtransmission 700during execution of the method 800 when the shift request is a high gearshift request. As can be seen, in this embodiment, at time t1, theengine 52 is controlled such as to reduce its torque output to a lowvalue (e.g., as close to zero as possible while the engine 52 isrunning). Similarly, at step 850, a torque of each of the clutches 204a, 204 b is reduced. In particular, the controller 500 controls the flowof transmission fluid to the clutches 204 a, 204 b such that neither ofthe shafts 400 a, 400 b is drivingly engaged by the clutches 204 a, 204b. For instance, the torque of the clutches 204 a, 204 b is reduced to akisspoint torque value of each of the clutches 204 a, 204 b. At thekisspoint torque values of the clutches 204 a, 204 b, the position ofeach of the clutches 204 a, 204 b is such that the clutch disks 250 andthe clutch plates 242 of each clutch 204 a, 204 b make initialfrictional contact with one another but do not yet transmit torque(i.e., they do not drive the respective shafts 400 a, 400 b).

Next, at step 860, the controller 500 controls the DCT 100 to shift thesubtransmission 700 to a neutral gear setting as shown at time t2 inFIG. 17 . In the neutral gear setting, the output shaft 740 is drivinglydisconnected from the input shaft 702. Notably, the high transmissiongear 730 on the input shaft 702 is drivingly disengaged from the inputshaft 702. Similarly, the low transmission gear 732 on the input shaft702 is drivingly disengaged from the input shaft 702. As such, in theneutral gear setting of the subtransmission 740, the output shaft 740 isnot driven by the input shaft 702 and therefore the output shaft 740 canrotate without being limited by the engaged gears of the DCT 100.

Subsequently, at step 870, with the subtransmission 700 operating in theneutral gear setting, the controller 500 selects one of the transmissiongears 600 mounted to either the shaft 400 a or the shaft 400 b to drivethe subtransmission 700 (via the layshaft 610 or 620) in order for theinput shaft 702 to turn, relative to the output shaft 740, at an inputshaft speed according to a gear ratio that will be implemented betweenthe input and output shafts 702, 740 by the high transmission gear 730if the shift request is a high gear shift request or the lowtransmission gear 732 if the shift request is a low gear shift request.In other words, the controller 500 selects one of the transmission gears600 of the main transmission 615 that will cause the input shaft 702 torotate at a speed adequate for either (i) the gear ratio implementedbetween the high transmission gears 730, 730′ when the shift request isa high gear shift request, or (ii) the gear ratio implemented betweenthe low transmission gears 732, 732′ when the shift request is a lowgear shift request. For example, if the shift request is a high gearshift request, the controller 500 selects a lower gear in the maintransmission 615 than the transmssion gear 600 currently engaged.Similarly, if the shift request is a low gear shift request, thecontroller 500 selects a higher gear in the main transmission 615 thanthe transmission gear 600 currently engaged. Once the appropriate one ofthe transmission gears 600 has been selected according to this criteria,the controller 500 shifts the main transmission 615 to engage theselected one of the transmission gears 600 to drive the subtransmission700. Notably, as can be seen in the example of FIG. 17 , the maintransmission 615 is downshifted at time t3. By rotating the input shaft702 at the appropriate speed, the vehicle 20 is safeguarded fromundergoing heavy shocks caused by a large speed differential between theinput shaft 702 and the output shaft 740.

With the correct gear engaged in the main transmission 615, the method800 then proceeds to step 880 where the controller 500 shifts thesubtransmission 700 to fulfill the shift request. In particular, thecontroller 500 shifts the subtransmission 700 from the neutral gearsetting to either the high transmission gear 730 if the shift requestwas a high gear shift request or the low transmission gear 732 if theshift request was a low gear shift request. For instance, in the exampleof FIG. 17 , at time t4, the subtransmission 700 is shifted to the hightransmission gear 730.

At step 890, which in this embodiment is performed at the same time asstep 880, a determination is made on a target engine speed at which theengine 52 should be running in order to maintain the speed of thevehicle 20 once the subtransmission 700 is shifted to the high or lowgear setting (step 880). In other words, the target engine speed isdetermined based on the current speed of the vehicle 20 and the engagedgears in the main transmission 615 and the subtransmission 700. Notably,the target engine speed approximately corresponds to the engine speedrequired for the output shaft 740 to rotate at an adequate speed, giventhe engaged gears on the main transmission 615 and the subtransmission700, to maintain the current speed of the vehicle 20. In particular, inthis embodiment, the target engine speed is the engine speed requiredfor the speed of the input shaft 702 to approximately match (i.e., beclose to but not be the same as) the speed of the output shaft 740considering the gear ratio implemented by the high transmission gears730, 730′ or the low transmission gears 732, 732′ engaged at step 880.For instance, an approximate match of the speeds may involve a speeddifference up to 50 rpm. For example, the target engine speed mayapproximately match the speed of the transmission gear 600 selected atstep 870. The small speed differential ensuing from the approximatespeed match may facilitate the engagement of a dog ring with the high orlow transmission gears 730, 732. Once the target engine speed isdetermined, if needed the engine 52 is then controlled to adjust theengine speed (i.e., to change a current engine speed to the targetengine speed). It is possible that in some cases, the engine speedrequires little to no adjustment. It is contemplated that, in someembodiments, step 890 could be performed before or after step 880.

It should be noted that should the shift request be made during launchof the vehicle 20, specifically where the first clutch 204 a is in aslip mode, the engine speed will not be synchronized in the presentembodiment. In such cases, the clutch 204 a is controlled in launchmode, with clutch pressure being gradually increased until clutch slipvanishes.

From step 890, the method 800 then proceeds to step 895 where control ofthe torque output of the engine 52 and the torque of the clutches 204 a,204 b is returned to the driver’s request at the accelerator 45. Inparticular, in this embodiment, as shown in FIG. 17 , at time t5, thetorque output of the engine 52 is increased according to a position ofthe accelerator 45, and the torque of the clutches 204 a, 204 b iscontrolled accordingly depending on the corresponding transmission gearsthat are engaged in the DCT 100. It should be understood that generally,at any one time, the torque of one of the clutches 204 a, 204 b will beat a driving torque value (i.e., a torque sufficient to drive thecorresponding shaft 400 a or 400 b) while the other one of the 204 a,204 b will be at a non-driving torque value (i.e., a torque insufficientto drive the corresponding shaft 400 a or 400 b) such as the kisspointtorque value thereof.

The method 800 then returns back to the initial step 810 with thevehicle 20 driving while the subtransmission 700 is operated in thenewly engaged high or low gear setting.

As will be understood from the above, during execution of the method800, the vehicle 20 is not required to stop moving while allowing thedriver to shift between the high and low gear settings. This can providea smoother driving experience for the driver as constantly stopping thevehicle 20 to shift between the high and low gear settings can beavoided. The method 800 can thus be performed in various drivingsituations, including for example when the vehicle 20 is creeping andduring a rock crawling session.

It is possible that during operation of the vehicle 20, the maintransmission 615 is shifted to a higher gear (i.e., upshifted) or alower gear (i.e., downshifted), for example to satisfy a driver’sacceleration request at the accelerator 45, and while the shifting isbeing performed, a driving situation changes that requires a reversal ofthe gear shift. This is particularly more probable because the vehicle20 is an off-road vehicle which is often operated in off-roadenvironments where driving situations tend to change more rapidly thanin a road driving environment. In a conventional vehicle equipped with aDCT, if the reversal of an upshift or downshift of the DCT is required,the initial gear shift must first be completed before the reversal ofthe gear shift can begin. This results in wasted time engaging a gearthat is no longer desired. Accordingly, with particular reference toFIGS. 18 to 20 , a method 900 for controlling the powertrain of thevehicle 20 in order to more efficiently reverse a gear shift will bedescribed herein.

As shown in FIG. 18 , the method 900 begins at step 910 where, when thevehicle 20 is operating with an “initial gear” engaged on one of theshafts 400 a, 400 b to drive the output shaft 740, the controller 500produces a first shift request for shifting the DCT 100 from the initialgear to a “different gear” engaged on another one of the shafts 400 a,400 b. In other words, the first shift request requires the shiftingfrom one of the transmission gears 600 engaged on the shaft 400 a or 400b to a higher or lower transmission gear 600 on the other shaft 400 a or400 b. For clarity and conciseness, the remainder of the method 900 willbe described with reference to the initial gear being the first gear 601on the shaft 400 a (and thereby driven by the first clutch 204 a), whilethe different gear requested by the first shift request is the secondgear 602 on the shaft 400 b. It is to be expressly understood that themethod 900 is not limited to a shift between the first and second gears601, 602 nor to reversing an upshift, as the method 900 can also beapplied to reversing a downshift.

In this example, the first shift request is produced by the controller500 based on the speed of the vehicle 20 and/or a torque output requiredfrom the engine 52. Notably, based on the speed of the vehicle 20 and/orthe torque output required from the engine 52, the controller 500determines that the DCT 100 should be upshifted to operate on the secondgear 602 and thus produces the first shift request. In other scenarios,the first shift request could be produced based on a signal receivedfrom a user-operated shifter (e.g., a paddle shifter) indicating thatthe driver wishes to perform the shift.

In response to the first shift request, at step 920, the controller 500executes a first shift sequence to shift the DCT 100 from the first gear601 to the second gear 602. An exemplary first shift sequence isillustrated in the graph of FIG. 19 which shows a torque of the engine52 and clutches 204 a, 204 b, a speed of the engine 52, and theengagement of the gears on shafts 400 a, 400 b while the first shiftsequence is being executed. The first shift sequence illustrated in FIG.19 corresponds to a “power shift” in which the DCT 100 is upshiftedwhile the vehicle 20 is accelerating. As shown in FIG. 19 , the firstshift sequence begins with a torque of the first clutch 204 a (whichdrives the shaft 400 a) being at a driving torque value, while a torqueof the second clutch 204 b (which is responsible for driving the shaft400 b) is at a non-driving torque value. The driving torque values ofthe clutches 204 a, 204 b are torque values at which the clutches 204 a,204 b drive the corresponding shafts 400 a, 400 b. The non-drivingtorque values of the clutches 204 a, 204 b are torque values at whichthe clutches 204 a, 204 b do not drive the corresponding shafts 400 a,400 b (e.g., the kisspoint torque values thereof).

With reference to FIG. 19 , according to the first shift sequence, attime t1′, the second gear 602 is engaged on the shaft 200 b. It shouldbe noted, that at this point, since the torque of the second clutch 204b is at the kisspoint torque value, the engagement of the second gear602 on the shaft 200 b does not cause the second gear 602 to drive theoutput shaft 740. Rather, as the torque of the first clutch 204 a is atthe driving torque value, it is still the first gear 601 that is drivingthe output shaft 740. At time t2′, the controller 500 begins decreasingthe torque of the first clutch 204 a to disengage the first clutch 204 afrom the engine 52. In this example, the torque of the first clutch 204a is decreased to the kisspoint torque value thereof or lower. At thesame time, the controller 500 begins increasing the torque of the secondclutch 204 b to engage the second clutch 204 b with the engine 52. Inthis example, the torque of the second clutch 204 b is increased to amicro-slip torque value thereof or higher. At their micro-slip torquevalues, the clutches 204 a, 204 b transmit the torque provided by theengine 52. As can be seen, at time t3′, a “torque handover” between thefirst and second clutches 204 a, 204 b is completed (i.e., the torque ofthe first clutch 204 a is at the non-driving torque value and the torqueof the second clutch 204 b is at the driving torque value) such that theoutput shaft 740 is being driven by the second gear 602 engaged on theshaft 400 b. Therefore, at time t3′, the speed of the engine 52 isadjusted in view of the change in the operating gear to maintain thespeed of the vehicle 20. More specifically, in this example, the speedof the engine 52 is decreased (since the main transmission 615 has beenupshifted) since maintaining the same speed of the engine 52 wouldotherwise cause a sudden increase in the speed of the vehicle 20.Correspondingly, the torque output of the engine 52 decreases. Tocompensate for this resulting decrease in torque output of the engine52, at time t3′, the second clutch 204 b begins being “overpressed”whereby the second clutch 204 b is operating at a torque value greaterthan the micro-slip torque value thereof. Once the torque output of theengine 52 recovers to the same torque output at which it was operatingprior to time t3′, at time t4′, the first gear 601 is disengaged fromthe shaft 400 a while the second gear 602 remains engaged on the shaft400 b. The torque of the second clutch 204 b is also returned tomicro-slip torque value thereof.

The full first shift sequence as described above and illustrated in FIG.19 is the regular shifting sequence when upshifting for example from thefirst gear 601 to the second gear 602. However, returning to FIG. 18 ,according to the method 900, at step 930, during execution of the firstshift sequence, the controller 500 produces a second shift request forshifting the DCT 100 from the second gear 602 to the first gear 601(i.e., from the “different gear” to the “initial gear”). In other words,the second shift request seeks the reversal of the first shift request.

The second shift request may be produced for different reasons. Forexample, in this embodiment, during execution of the first shiftsequence, the controller 500 may detect an operational change related tooperation of the vehicle 20, and subsequently determine that theoperational change requires engagement of the first gear 601. Thecontroller 500 thus produces the second shift request in view of thatdetermination. For instance, the operational change may be a suddenbraking of the vehicle 20, a release of the accelerator 45 by thedriver, or a jump event experienced by the vehicle 20 (e.g., sensed byan accelerometer), or any other suitable event. In some cases, thesecond shift request may be produced as a result of receiving a signal,by the controller 500, from a user-operated shifter (e.g., a paddleshifter) indicating that the driver wishes to perform the shift.

The method 900 thus proceeds to step 940 where, in response to thesecond shift request, the controller 500 interrupts the first shiftsequence prior to the first shift sequence having finished. In otherwords, the first shift sequence is interrupted before the first gear 601is disengaged on the shaft 400 b (time t4′ in FIG. 19 ). The timing ofthe interruption of the first shift sequence is dependent on a time atwhich the second shift request is produced. With reference to FIG. 19 ,two alternative interruption times i1, i2 for interrupting the firstshift sequence will be described herein. A first interruption time i1takes place at any point between times t2′ and t3′. Notably, the firstinterruption time i1 takes place during the torque handover between thefirst and second clutches 204 a, 204 b. Alternatively, a secondinterruption time i2 takes place at any point between times t3′ and t4′.In particular, the second interruption time i2 takes place whiledecreasing the speed of the engine 52.

The remainder of the method 900 will now be described with regard tointerrupting the first shift sequence at the first interruption time i1.A description of the remainder of the method 900 will then be providedwith regard to interrupting the first shift sequence at the secondinterruption time i2.

When the first shift sequence is interrupted at the first interruptiontime i1 (i.e., before adjusting the speed of the engine 52), theinterruption of the first shift sequence consists of the controller 500stopping the decreasing of the torque of the first clutch 204 a beforethe torque of the first clutch 204 a reaches the kisspoint torque valuethereof. At the same time, the controller 500 stops the increasing ofthe torque of the second clutch 204 b before the torque of the secondclutch 204 b reaches the micro-slip torque value thereof. In otherwords, the controller 500 stops the torque handover between the clutches204 a, 204 b. With the execution of the first shift sequence beinginterrupted before its completion, the method 900 then proceeds to step950 (FIG. 18 ) whereby, in response to the second shift request, thecontroller 500 executes a second shift sequence to reverse the firstshift sequence such that the DCT 100 engages the first gear 601 fordriving on the shaft 400 a.

The steps of the second shift sequence will be described herein withreference to FIG. 20 which illustrates a complete shift sequence fordownshifting the main transmission 615, namely to shift the DCT 100 fromthe second gear 602 to the first gear 601 while the vehicle 20accelerates. That is, the second shift sequence illustrated in FIG. 20corresponds to a “power shift” in which the DCT 100 is downshifted whilethe vehicle 20 is accelerating. However, the second shift sequenceexecuted in this context comprises selected steps of the shift sequenceshown in FIG. 20 as will be understood from the below description.

With reference to FIG. 20 , when the first shift sequence is interruptedat the first interruption time i1, the second shift sequence begins at afirst start time s1. Notably, at the first start time s1, the controller500 begins decreasing the torque of the second clutch 204 b to at leastits kisspoint torque value and increasing the torque of the first clutch204 a to at least its micro-slip torque value. As such, the torquehandover between the first and second clutches 204 a, 204 b that wasinitiated during the first shift sequence (FIG. 19 ) is reversed.According to the second shift sequence, the controller 500 alsomaintains the first gear 601 engaged on the shaft 400 a, as opposed todisengaging the first gear 601 as is done at time t4′ in the first shiftsequence. Once the driving torque is returned to the first clutch 204 aand the torque of the second clutch 204 b is decreased to a non-drivingtorque, the second shift sequence finishes by disengaging the secondgear 602 on the shaft 400 b. With the second shift sequence completed,the method 900 finishes as the first shift request was reversed withoutfirst completing the first shift sequence.

Returning now to FIG. 19 , if at step 940, the first shift sequence isinterrupted at the second interruption time i2 instead of the firstinterruption time i1, the controller 500 interrupts the first shiftsequence during the adjusting of the speed of the engine 52 by stoppingthe adjusting of the speed of the engine 52. More specifically, in thisexample, the controller 500 stops the decreasing of the speed of theengine 52. While in this example the second interruption time i2 isduring the decrease of the speed of the engine 52, it is contemplatedthat, in other examples, depending on when the second shift requesttakes place, the second interruption time i2 could be once the speed ofthe engine 52 has already been fully decreased. With the execution ofthe first shift sequence interrupted before its completion, the method900 then proceeds to step 950 (FIG. 18 ) whereby, in response to thesecond shift request, the controller 500 executes the second shiftsequence to reverse the first shift sequence. As the first shiftsequence is interrupted at a different time than that described above inrespect of the first interruption time i1, the second shift sequence isdifferent from that described above.

With reference to FIG. 20 , when the first shift sequence is interruptedat the second interruption time i2, the second shift sequence begins ata second start time s2. Notably, at the second start time s2, the secondshift sequence begins by increasing the speed of the engine 52 to aspeed that is appropriate for driving the first gear 601. Afterincreasing the speed of the engine 52, the torque handover between theclutches 204 a, 204 b which was effected in the first shift sequence isreversed. More specifically, in the second shift sequence, afterincreasing the speed of the engine 52, the controller 500 lowers thetorque of the second clutch 204 b to at least the kisspoint torque valuethereof and increases the torque of the first clutch 204 a to at leastthe micro-slip value thereof. The remainder of the second shift sequenceis then completed as described above with regard to the first start times1.

As such, after having concluded the step 950, the shift from the firstgear 601 to the second gear 602 has been reversed before the completionof the first shift sequence. As will be appreciated, this can save timefor reversing a gear shift compared to conventional methods such thatthe correct gear will be engaged in a timelier manner. For instance, insome cases, this may add up to about 0.3 to 0.4 seconds of time saved.Furthermore, the reversal of the gear shift is not noticeable by thedriver and thus does not negatively affect the smoothness of the ride ofthe vehicle 20.

Although in the example provided above the first shift request is for anupshift and the second shift request is for a downshift, it will beunderstood that the method 900 can be performed for the oppositescenario where the first shift request is for a downshift and the secondshift request is for an upshift. In that scenario, the graph of FIG. 20would correspond to the “first shift sequence”, and the start times s1,s2 would be the first and second interruption times while the times i1,i2 in FIG. 19 would correspond to the start times for the second shiftsequence to reverse the first shift sequence. For a better understandingof this scenario, a brief description of the full shift sequence shownin FIG. 20 will be provided herein.

With reference to FIG. 20 , according to this shift sequence fordownshifting the main transmission 615 from the second gear 602 to thefirst gear 601, at time t1″, the first gear 601 is engaged on the shaft400 a. It should be noted, that at this point, since the torque of thefirst clutch 204 a is at the kisspoint torque value, the engagement ofthe first gear 601 on the shaft 400 a does not cause the first gear 601to drive the output shaft 740. Rather, as the torque of the secondclutch 204 a is at the driving torque value, it is still the second gear602 that is driving the output shaft 740. At the same time t1″, thespeed of the engine 52 is increased to prepare for driving engagement ofthe first gear 601, and the controller 500 momentarily reduces thetorque of the second clutch 204 b to allow some slip to occur at thesecond clutch 204 b in order to compensate for the increased enginespeed. At time t2″, with the speed of the engine 52 increased, thetorque handover between the clutches 204 a, 204 begins. Notably, thecontroller 500 increases the torque of the first clutch 204 a from thenon-driving torque value thereof to a driving torque value (in thisexample the micro-slip torque value) to engage the first clutch 204 bwith the engine 52, and decreases the torque of the second clutch 204 bfrom the driving torque value thereof (in this example the kisspointtorque value) to disengage the second clutch 204 b from the engine 52.Subsequently, at time t3″, with the torque handover between the clutches204 a, 204 b completed, the controller 500 controls the DCT 100 todisengage the second gear 602 on the shaft 400 b in order to reducefriction, while the first gear 601 remains engaged on the shaft 400 a.

As mentioned above, when the first shift sequence corresponds to theshift sequence of FIG. 20 , the time at which the controller 500interrupts the first shift sequence at step 940 can be either the times1 or the time s2. If the chosen interruption time is time s1, theinterruption of the first shift sequence comprises stopping theincreasing of the torque of the first clutch 204 a and stopping thedecreasing of the torque of the second clutch 204 b. The second shiftsequence executed at step 950 then begins at time i1 in the graph ofFIG. 19 . Notably, this includes reversing the initiated torque handoverbetween the clutches 204 a, 204 b, reducing the speed of the engine 52at time t3′ once the torque handover has been reversed, and at time t4′,disengaging the first gear 601 on the shaft 400 a to reduce frictionwhile maintaining the second gear 602 engaged on the shaft 400 b.

Alternatively, if the chosen interruption time in the shift sequence ofFIG. 20 is time s2, the interruption of the first shift sequencecomprises stopping the increasing of the speed of the engine 52. Thesecond shift sequence executed at step 950 then begins at time i2 in thegraph of FIG. 19 . Notably, this includes decreasing the speed of theengine 52 in order to maintain the speed of the vehicle 20 andsubsequently, at time t4′, disengaging the first gear 601 on the shaft400 a to reduce friction while maintaining the second gear 602 engagedon the shaft 400 b.

As will be appreciated, the method 900 can be performed when shiftingfrom any two adjacent gears, whether initially upshifting ordownshifting.

A method 1000 for accelerating the vehicle 20 from rest will now bedescribed with reference to FIGS. 21 and 22 . The method 1000 asdescribed herein seeks to provide a selectable mode in which thepowertrain of the vehicle 20 can be operated to obtain a fasteracceleration of the vehicle 20 from rest, thereby providing the vehicle20 with a greater 0-100 km/h performance than in a standard operationmode. Some conventional vehicles are provided with a launch control modefor a similar purpose, however the implementation of this mode typicallyseeks to limit spinning of the driving wheels of the vehicle. While thismay be suitable for a road vehicle, off-road vehicles such as thevehicle 20 tend to perform better when their driving wheels areslipping, and therefore conventional launch control modes are not idealfor an off-road vehicle.

With reference now to FIG. 21 , the method 1000 begins at step 1010 withthe powertrain being controlled according to a standard controlstrategy. The standard control strategy corresponds to a standardoperation mode of the powertrain, where no specific out-of-routinecontrol strategy is being implemented. At subsequent step 1020, whilethe vehicle 20 is at rest, the controller 500 receives a mode indicationfrom a mode actuator 505 (FIGS. 2, 15 ) indicating that the driver ofthe vehicle 20 has selected a launch control mode for accelerating thevehicle 20 from rest. It is to be understood that, at step 1020, thevehicle 20 is defined as being at rest if the vehicle 20 is immobile(i.e., brake pedal actuated), with the engine 52 running, and a forwarddrive gear engaged by the gear shifter 56 (i.e., in this embodiment,specifically in the high gear setting). These may be referred to asinitial mode conditions which must be satisfied to enable the modeactuator 505. In other words, if these initial mode conditions are notmet, the mode actuator 505 does not generate the mode indication whenactuated. As shown in FIG. 15 , the mode actuator 505 is incommunication with the controller 500. In this embodiment, as shown inFIG. 2 , the mode actuator 505 is disposed on or near a dashboard of thevehicle 20 for operation by the driver. The mode actuator 505 may be abutton or any other suitable user-operator actuator (e.g., a switch).The user can let go of the mode actuator 505 once it has been actuated.

Once the mode indication is received, the method 1000 proceeds to step1030 where the controller 500 validates if the conditions for engagingthe launch control mode are satisfied. In particular, the controller 500validates that it receives a brake-on indication from a braking systemsensor 515 (see FIG. 15 ) indicating that the braking system of thevehicle 20 has been activated. In this embodiment, the braking system isactivated when the brake pedal (not shown) is held down by the driver toimmobilize the vehicle 20. The controller 500 also verifies that thespeed of the vehicle 20 is null. At step 1030, the controller 500 alsodetermines if the accelerator 45 is positioned at its launch controlacceleration position. In this embodiment, the accelerator 45 isactivated for launch control acceleration when the accelerator pedal 45is held down by the driver. Notably, in this embodiment, as shown inFIG. 15 , the controller 500 is in communication with an acceleratorsensor 517 which sends a signal to the controller 500 indicative of aposition of the accelerator 45. In this embodiment, the launch controlacceleration position of the accelerator 45 corresponds to a position atwhich the accelerator 45 requests an acceleration equal to or greaterthan a predetermined acceleration threshold. For instance, in thisembodiment, the predetermined acceleration threshold is 40% of themaximum acceleration that can be requested by the accelerator 45. Thepredetermined acceleration threshold may be greater in other embodiments(e.g., 60%, 80% of the maximum acceleration that can be requested). Inyet other embodiments, the predetermined acceleration threshold may be100% of the maximum acceleration. In other words, the launch controlacceleration position of the accelerator 45 corresponds to the positionat which the accelerator 45 requests the maximum acceleration providedby the engine 52. That is, the launch control acceleration position ofthe accelerator 54 may be the maximum acceleration position of theaccelerator 45. In this embodiment, the maximum acceleration position ofthe accelerator 45 corresponds to the accelerator pedal being fullypressed by the driver. The controller 500 may also validate that the DCT100 is engaged in the high gear setting. If the controller 500determines that one of these conditions is not met, the method 1000restarts at step 1010. The controller 500 may trigger an alert to informthe driver of the denial of operation in the launch control mode. Forinstance, in this embodiment, the controller 500 causes the displayelement 805 (FIG. 15 ) or a different display element visible to thedriver to display an indication to the driver indicative of the denialof operation in the launch control mode. In this example, the displayelement 805 is an icon on a display screen disposed on the dashboard ofthe vehicle 20. In other embodiments, the alert triggered controller 500may be an audio signal instead of visual signal (e.g., an alert soundplayed by a speaker).

Furthermore, in some embodiments, subsequent to receiving the modeindication and prior to receiving the brake-off indication, thecontroller 500 verifies one or more pre-launch deactivation conditionson the basis of which the controller 500 returns to the standardoperation mode of the powertrain (i.e., aborting the launch of thevehicle 20 in the launch control mode). For instance, one of thepre-launch deactivation conditions may relate to a time limit forreceiving the brake-on indication. Notably, in some embodiments, thecontroller 500 determines if a time limit (e.g., 10 seconds) countedfrom the moment the mode indication was received has been reached. Ifthe time limit has been reached, the controller 500 determines that thepre-launch deactivation condition has been met. In some embodiments, oneof pre-launch deactivation conditions may relate to a temperature of thetransmission fluid of the DCT 100 (i.e., the transmission fluid that isrouted to the clutches 204 a, 204 b for actuation thereof). Inparticular, the controller 500 determines if the temperature of thetransmission fluid is equal to or greater than a predeterminedtemperature threshold. If the temperature of the transmission fluid isequal to or greater than the predetermined threshold, the controller 500determines that the pre-launch deactivation condition has been met. Atemperature sensor 519 (FIG. 15 ) in communication with the controller500 transmits signals to the controller 500 representative of thetemperature of the transmission fluid. Once the controller 500determines that one or more of the pre-launch deactivation conditionshave been met, the controller 500 returns to the standard operationmode.

In some additional or alternative embodiments, one of pre-launchdeactivation conditions could relate to a temperature of the clutchdisks 250. In particular, the controller 500 determines if thetemperature of the clutch disks 250 is less than a predeterminedclutch-related temperature threshold. Determining or estimating thetemperature of the clutch disks 250 is contemplated according to avariety of known methods and is not meant to be particularly limited. Ifthe temperature of the clutch disks 250 is less than the predeterminedthreshold, the controller 500 determines that the pre-launchdeactivation condition has been met. Once the controller 500 determinesthat one or more of the pre-launch deactivation conditions have beenmet, the controller 500 returns to the standard operation mode.

If the controller 500 validates that the launch control conditions aremet (and, optionally that the pre-launch deactivation conditions havenot been met), the method 1000 proceeds to step 1040 where, in responseto receiving at least the mode indication and the brake-on indicationand determining that the accelerator 45 is in the launch controlacceleration position, the powertrain is controlled according to thelaunch control mode which is implemented by a launch control strategythat is different from the standard control strategy. The launch controlstrategy, which begins at time t_(A), is illustrated in greater detailin the graph of FIG. 22 . With the accelerator 45 at an activatedposition, under normal conditions, the speed of the engine 52 wouldincrease relatively quickly. Under the launch control strategy, theengine 52 is controlled, by a launch control rev limiter at time t_(A),in order to limit the speed of the engine 52 to an increased yet limitedengine idle speed S_(L) that is greater than an idle speed SI of theengine 52 in the standard control strategy and without activation of theaccelerator 45. It is noted that the term “idle” is used herein toindicate operation of the engine 52 without driving or causing movementof the vehicle 20. The launch control rev limiter function limits theengine speed according to the actual position of the accelerator 45. Asone non-limiting example, for a 40% pedal position, the limit is 3,000RPM; for 100% the limit is 5,000 RPM; it is contemplated these valuescould vary. In the present embodiment, the engine speed is limited usingignition control, such that the throttle valve is open and air inputflow is unimpeded, providing for the engine 52 to quickly increase itsspeed when the limiter is removed. In this embodiment, the increase ofthe speed of the engine 52 to the limited speed S_(L) causes theturbocharger 57 (FIG. 3 ) to provide additional boost pressure to theengine 52. This may further optimize the acceleration of the vehicle 20in the launch control mode.

Prior to activation of the launch control strategy with the vehicle 20immobile and the engine 52 running, as shown in FIG. 22 , the torque ofthe first clutch 204 a is at about the kisspoint torque value thereof;the torque of the second clutch 204 b is zero. With commencement of thelaunch control strategy at time t_(A), the pressure of the first clutch204 a is increased to slightly above the kisspoint torque value thereof;the torque of the second clutch 204 b remains zero.

While the powertrain is being controlled according to the launch controlstrategy, the controller 500 receives, at time t_(B) in FIG. 22 , abrake-off indication indicating that the braking system has beenreleased. In this embodiment, the brake-off indication is transmitted tothe controller 500 by the braking system sensor 515 when the driver letsgo off the brake pedal. In response to receiving the brake-offindication, the method proceeds to step 1060, with the controller 500increasing the torque of the first clutch 204 a according to apredefined ramp to drive the first gear 601 on the shaft 400 a. As willbe understood, the first gear 601 corresponds to the lowest gear on theshaft 400 a and therefore the acceleration of the vehicle 20 begins withthe first gear 601 engaged. In this embodiment, the predefined ramp(i.e., rate) according to which the torque of the first clutch 204 a isincreased at time t_(B) is steeper than a standard ramp according towhich the torque of the first clutch 204 a is increased in the standardcontrol strategy. The rapid increase in the torque of the clutch 204 acan cause the vehicle 20 to accelerate even more rapidly as the firstgear 601 drives the output shaft 740. In other embodiments, thepredefined ramp according to which the torque of the first clutch 204 ais increased at time t_(B) is the same or approximately the same as thestandard ramp according to which the torque of the first clutch 204 a isincreased in the standard control strategy.

Once clutch slip for the first clutch 204 a decreased to a predeterminedthreshold, e.g. 50% clutch slip, the launch control rev limiter isremoved at step 1065 of the method 1000 at a time t_(E) furtherillustrated in FIG. 22 . It is noted that standard rev limiters used tocontrol engine speed to prevent engine damage will generally remainactive when the launch control rev limiter is removed.

The engine 52 is then controlled to increase the speed thereof accordingto the launch control acceleration position of the accelerator 45. Inother words, the throttle valve that regulates air intake into theengine 52 opens according to the position of the accelerator 45.Therefore, the throttle valve remains opens at its positioncorresponding to the position of the accelerator 45 and ignition timingis returned to normal in order for the engine 52 to provide acorresponding acceleration. Notably, the increased engine idle speed andincreased torque of the clutch 204 a performed at step 1040 can alreadyensure on their own a more rapid acceleration of the vehicle 20 fromrest.

By this point, the vehicle 20 has undergone a significant accelerationfrom rest that would not otherwise be possible in the standard controlstrategy.

Following time t_(E), the torque gradient of the first clutch 204 a isdecreased, such that the torque increases at a lesser rate. When theclutch slip of the first clutch 204 a substantially reaches zero, at atime t_(F), the launch control mode/strategy ends and the vehicle 20returns to normal control conditions. At this point, in this embodiment,the method 1000 proceeds to step 1100 where the powertrain is returnedto operating in the standard operation mode.

In at least some embodiments, as the speed of the engine 52 reaches atop speed ST that is short of the redline engine speed, at time tc inFIG. 22 , optionally, the vehicle 20 can be rapidly shifted from thefirst gear 601 to the second gear 602. It is noted that the shift tosecond gear 602 occurs with the powertrain operating in the standardoperation mode. This is done by effecting the torque handover betweenthe clutches 204 a, 204 b. In particular, when the controller 500determines that the vehicle 20 will be shortly shifted to the secondgear 602, the pressure of the second clutch 204 b is increased to thekisspoint. Then at the time tc, the torque of the first clutch 204 a isdecreased to the predetermined non-driving torque value or lower, whilethe torque of the second clutch 204 b is increased to drive the secondgear 602. As the torque handover between the clutches 204 a, 204 b istaking place, the speed of the engine 52 is momentarily decreased toeffect a smooth transition to the second gear 602. Thus, at time t_(D)shortly after time t_(C), the vehicle 20 is driving with the second gear602 engaged.

It is contemplated that, in some embodiments, while controlling thepowertrain according to the launch control strategy, the controller 500could monitor different operational parameters to verify if it is stillappropriate to remain in the launch control strategy. For instance, insome embodiments, the controller 500 could determine if one or moredeactivation conditions have been met, and if they have, the controller500 could subsequently return to the standard operation mode at step1010 to operate the powertrain in the standard control strategy. Forexample, in this embodiment, one of the deactivation conditions is atime limit. Notably, in response to the controller 500 determining thatthe time limit of controlling the powertrain according to the launchcontrol strategy has been reached, the launch control mode is exited andthe powertrain is again operated in the standard operation mode. In someembodiments, another deactivation condition could be if the brakingsystem is activated. For instance, while in the launch control mode, thecontroller 500 detects that the braking system is activated, the method1000 could end the launch control strategy and return to step 1010. Insome embodiments, another deactivation condition could be a decrease inthe position of the accelerator 45. Notably, if while in the launchcontrol mode, the controller 500 detects that the position of theaccelerator 45 has decreased (e.g., the driver has let go of theaccelerator 45), the controller 500 could end the launch controlstrategy and the method 1000 returns to step 1010. In some embodiments,another deactivation condition could be related to a time limit forreceiving the brake-off indication while at step 1040. For instance, ifwhile in the launch control mode at step 1040, a predetermined amount oftime passes without having received the brake-off indication indicatingthat the driver has let go of the brake pedal, the controller 500 couldend the launch control strategy and the method 1000 returns to step1010. In some embodiments, another deactivation condition could berelated to actuation of the mode actuator 505. For instance, if while inthe launch control mode, the controller 500 receives a signal from themode actuator 505 indicating that the driver has pressed the modeactuator 505, the controller 500 could end the launch control strategyand the method 1000 returns to step 1010. In some embodiments, anotherdeactivation condition could be related to the shifting to the secondgear 602.

While the above methods 800, 900, 1000 have been described as beingexecuted in part or in their entirety by the controller 500, it is to beunderstood that the controller 500 could be in communication with othercontrollers to perform one or more of the methods 800, 900, 100. Forinstance, in order to control the engine 52, the controller 500 could bein communication with the ECU that controls the engine 52 and transmitand/or receive signals therefrom in order to perform the methods 800,900, 1000.

Modifications and improvements to the above-described implementations ofthe present technology may become apparent to those skilled in the art.The foregoing description is intended to be exemplary rather thanlimiting. The scope of the present technology is therefore intended tobe limited solely by the scope of the appended claims.

What is claimed is:
 1. A method for controlling a powertrain of avehicle, the powertrain comprising: an internal combustion engine; and adual-clutch transmission operatively connected to the engine, thedual-clutch transmission comprising: a first clutch and a second clutchselectively actuated to transmit motion from the engine to a first shaftand a second shaft respectively; at least one first gear mounted to thefirst shaft; at least one second gear mounted to the second shaft, theat least one first gear and the at least one second gear defining inpart a main transmission of the dual-clutch transmission; and asubtransmission operatively connected to the main transmission, thesubtransmission comprising: an input shaft; a high transmission gear anda low transmission gear mounted to the input shaft, the hightransmission gear and the low transmission being selectively engageableto place the subtransmission in a high transmission setting and a lowtransmission setting respectively; and an output shaft operativelyconnected to the input shaft by a selected one of the high transmissiongear and the low transmission gear, the method comprising: operating thedual-clutch transmission while the vehicle is in motion with one of thehigh transmission gear and the low transmission gear drivingly engagedto the input shaft; during said operating, receiving a shift request toengage an other one of the high transmission gear and the lowtransmission gear to the input shaft in order to drive the output shaftwith the other one of the high transmission gear and the lowtransmission gear; in response to the shift request: reducing a torqueoutput of the engine and a torque of at least one of the first andsecond clutches; shifting the subtransmission to a neutral gear settingwhereby the output shaft is drivingly disconnected from the input shaft;after shifting the subtransmission to the neutral gear setting,selecting one of the at least one first gear and the at least one secondgear to drive the subtransmission in order for the input shaft to turn,relative to the output shaft, at an input shaft speed according to agear ratio that would be implemented between the input and output shaftsby the other one of the high transmission gear and the low transmissiongear; shifting the main transmission to engage the selected one of theat least one first gear and the at least one second gear to drive thesubtransmission; after shifting the main transmission, shifting thesubtransmission to the other one of the high transmission gear and thelow transmission gear; and after shifting the subtransmission to theother one of the high transmission gear and the low transmission gear,controlling the torque output of the engine and the torque of the firstand second clutches according to a driver request at an accelerator ofthe vehicle.
 2. The method of claim 1, further comprising: determining atarget engine speed required to maintain a speed of the vehicle when theselected one of the at least one first and the at least one second gearis drivingly engaged; and controlling the engine to change a currentengine speed to the target engine speed.
 3. The method of claim 1,further comprising, after shifting the subtransmission to the other oneof the high transmission gear and the low transmission gear but prior tocontrolling the torque output of the engine and the torque of the firstand second clutches according to the driver request: controlling theengine to change a current engine speed to approximately match a speedof the selected one of the at least one first gear and the at least onesecond gear.
 4. The method of claim 1, wherein: in response to the shiftrequest being for engaging the low transmission gear to the input shaft,the method further comprises: comparing an operating speed associatedwith the vehicle to a predetermined speed; and denying the shift requestin response to the operating speed associated with the vehicle beinggreater than the predetermined speed.
 5. The method of claim 1, wherein:in response to the shift request being for engaging the hightransmission gear to the input shaft, the method further comprises:comparing an operating speed associated with the vehicle to apredetermined speed; comparing the torque output of the engine to apredetermined engine torque; denying the shift request in response to:the operating speed associated with the vehicle being less than or equalto the predetermined speed; and the torque output of the engine beinggreater than the predetermined engine torque.
 6. The method of claim 4,further comprising, after denying the shift request, displaying anindication to a driver of the vehicle indicative of a denial of theshift request.
 7. A vehicle comprising: a frame; a driver seat connectedto the frame; a plurality of ground-engaging wheels operativelyconnected to the frame; a powertrain comprising: an internal combustionengine supported by the frame; and a dual-clutch transmissionoperatively connected to the engine, the dual-clutch transmissioncomprising: a first clutch and a second clutch selectively actuated totransmit motion from the engine to a first shaft and a second shaftrespectively; at least one first gear mounted to the first shaft; atleast one second gear mounted to the second shaft, the at least onefirst gear and the at least one second gear defining in part a maintransmission of the dual-clutch transmission; and a subtransmissionoperatively connected to the main transmission, the subtransmissioncomprising: an input shaft; a high transmission gear and a lowtransmission gear mounted to the input shaft, the high transmission gearand the low transmission being selectively engageable to place thesubtransmission in a high transmission setting and a low transmissionsetting respectively; and an output shaft operatively connected to theinput shaft by a selected one of the high transmission gear and the lowtransmission gear, the output shaft being operatively connected to atleast one of the plurality of ground-engaging wheels; and a controllerin communication with the engine and the dual-clutch transmission, thecontroller being configured to perform a method comprising: operatingthe dual-clutch transmission while the vehicle is in motion with one ofthe high transmission gear and the low transmission gear drivinglyengaged to the input shaft; during said operating, receiving a shiftrequest to engage an other one of the high transmission gear and the lowtransmission gear to the input shaft in order to drive the output shaftwith the other one of the high transmission gear and the lowtransmission gear; in response to the shift request: reducing a torqueoutput of the engine and a torque of each of the first and secondclutches; shifting the subtransmission to a neutral gear setting wherebythe output shaft is drivingly disconnected from the input shaft; aftershifting the subtransmission to the neutral gear setting, selecting oneof the at least one first gear and the at least one second gear to drivethe subtransmission in order for the input shaft to turn, relative tothe output shaft, at an input shaft speed according to a gear ratio thatwould be implemented between the input and output shafts by the otherone of the high transmission gear and the low transmission gear;shifting the main transmission to engage the selected one of the atleast one first gear and the at least one second gear to drive thesubtransmission; after shifting the main transmission, shifting thesubtransmission to the other one of the high transmission gear and thelow transmission gear; and after shifting the subtransmission to theother one of the high transmission gear and the low transmission gear,controlling the torque output of the engine and the torque of the firstand second clutches according to a driver request at an accelerator ofthe vehicle.
 8. The vehicle of claim 7, wherein the vehicle is anoff-road vehicle.